Combination mooring system

A combination mooring system for mooring a floating vessel to an offshore structure is disclosed. When a loading force induced by wind, waves, ice, or ocean currents does not act against the vessel, the mooring system is at a mean position. As a loading force urges the vessel away from the structure, the mooring system adapts to accommodate movement of the vessel relative to the structure. To counteract movement of the mooring system from its mean position, a buoy connected by a cable to the mooring system is progressively submerged. As the buoy is submerged, it provides a buoyant restoring force which counteracts the loading force acting on the vessel. When the loading force subsides, the buoyant restoring force urges the mooring system toward its mean position. In a preferred embodiment, the mooring system has a stop which limits the excursion of the mooring system from its mean position. Therefore, if the displacing force should exceed the buoyant restoring force, the stop will convert the adaptable mooring system to a rigid mooring system capable of handling extreme loading forces.